<html>
 <body>
  <h2>This Sudoku is not valid</h2>
  <p>
   This Sudoku <b>hasn't a unique solution</b>: the number of clues (cells with a
   value) is too small.
  </p><p>
   The minimum number of clues must be 17. Sudokus with 16 clues or
   less all have more than one solution. This Sudoku has only <b>{0}</b> clues.
  </p>
 </body>
</html>